Many scholars of politics have proven that two party systems are the best, but in my opinion I don’t think it is the best because it doesn’t really give room for proper democracy.
Good democracy as said earlier by you is achieved through good challenges and prove of self and political worth
or benefits that can be derived if the opportunity is given.
Witness of two-person is asserted to be true, so democracy can be well achieved with the two-party system.
You even get to realize that, bringing multiple parties together, all others tend to support one of the two
thereby making democracy more interesting when played by two sides or political parties.